After import CSV calender in SharedMailbox only I can see all items

I'v imported a CSV file with Calendaritems in a SharedMailbox Calendar in Outlook.

File > Open > import/export

Works fine, but only I can see all the items, not all others.

Then:

When deleting the calendar in my Outlook and then add the calender again, no items show up.
What's going on? 

Please some help. Thanks